Field of the Invention
The present invention relates to a push switch that is configured to close an electrical circuit by performing a stroke movement of a movable contact point, which is arranged to be spaced from a fixed contact point, on an opposing line thereof to make contact with each other.
Description of the Related Art
For example, Japanese Patent Laid-Open Publication No. 2000-62528 discloses this kind of conventional push switches. This push switch relates to a brake switch attached to a brake pedal for a vehicle, wherein a push rod that is pushed down into a casing causes a movable contact point to be separated from a fixed contact point in a mounting state, and when a brake pedal is depressed, the push rod is in a state of being movable in an outward direction of the casing, and the movable contact point urged by a contact pressure spring moves to be in contact with the fixed contact point.
Incidentally at the operating of the push switch, the respective opposing surfaces of the contact points become closer or away in a perpendicular direction with each other. In many cases, however, abrasion powder caused by the operation is interposed between the opposing surfaces of the movable contact point and the fixed contact point or arc is generated between the contact points to accumulate carbides or oxides to form an insulating film thereon. In this case, a so-called contact failure is generated to bring in operation instability.
Therefore, in the conventional push switch as mentioned above, a contact piece is formed in a paired cantilever shape obliquely extending in a direction of being closer to the fixed contact point from the central flat plate section, and the moving contact points are provided in tip ends thereof to oppose a pair of the fixed contact points and are urged in a direction of the fixed contact points by the contact pressure spring. Therefore at the time the moving contact point makes contact with the fixed contact point, the moving contact point is configured to make elastic contact with the fixed contact point by a predetermined pressure.
In addition, at the time of the elastic contact between the contact points, the cantilever shape section in the contact piece is deflected by an urging force of the contact pressure spring, and therefore the movable contact point slides by a slight distance on the fixed contact point outwardly. Thereby a wiping operation on the contact surfaces of the contact points of each other is performed to eliminate foreign objects such as abrasion powder, carbides, oxides and the like.
In the conventional push switch as mentioned above, however, since the cantilever shaped section of the contact piece is in a free state before the elastic contact of the contact points, the contact pressure between the contact points has no other choice of starting with an initial value of zero, and as usual, it is not possible to avoid the arc generation between the contact points to be caused by a wobbly movement of the contact piece at the contacting of the contact points. In addition, a displacement of the movable contact point is caused only by a deflection of the cantilever shaped section and a sliding amount thereof is small. Therefore it is not sufficient for the effective wiping operation.